Restore Your GM Truck’s Performance and Reliability
Is your 2003 TrailBlazer EXT or another GM truck acting up? Dealing with a frustrating no-start condition, erratic engine behavior, or a persistent Check Engine Light can bring your day to a halt. As a technician with over 20 years of experience, I’ve seen countless vehicles sidelined by a failing Powertrain Control Module (PCM). This isn’t just a part; it’s the central computer of your engine, managing everything from fuel injection and ignition timing to transmission shifts. When it fails, the symptoms can be confusing and widespread.
This replacement PCM, part number 89017734, is the definitive solution to get your vehicle running correctly again. We take the guesswork and hassle out of the repair by pre-programming the module specifically for your vehicle using your VIN. This means it arrives with the latest GM software updates, ready for a straightforward installation. You get a reliable fix that restores factory performance without the expensive trip to a dealership for programming.
A Technician’s Notebook: The Intermittent No-Start Nightmare
I remember a 2005 Silverado that came into my bay with a ghost of a problem. The owner said it would randomly refuse to start, but after a few tries, it would fire up and run perfectly for days. He had already replaced the battery, starter, and ignition switch. We checked fuel pressure and spark—both were fine when it was running. The challenge was catching it in the act of failing. After two days, it finally happened. We connected the scanner and found a P0601 code (Internal Control Module Memory Check Sum Error) stored. The PCM’s internal processor was failing intermittently, causing the no-start. We installed a VIN-programmed PCM, performed the security relearn, and the truck never had the issue again. It’s a classic example of how a failing 2003 TrailBlazer EXT PCM or similar module can create symptoms that mislead even experienced DIYers.
Common Signs of a Failing PCM
If your vehicle’s computer is on its way out, you might be experiencing one or more of these issues. A faulty 2003 TrailBlazer EXT PCM can be the root cause of many frustrating drivability problems. Look out for:
- ✔ Check Engine Light is on with codes like P0601, P0606, or U0100.
- ✔ Engine stalling or misfiring for no apparent reason.
- ✔ Vehicle will not start, or has difficulty starting.
- ✔ Noticeable decrease in fuel economy.
- ✔ Harsh or erratic automatic transmission shifting.
- ✔ Communication errors with your OBD-II scan tool.
- ✔ Other modules (like ABS or BCM) setting communication loss codes.
A Straightforward Guide to Installation
Replacing the PCM is a manageable job for a confident DIYer. Our pre-programming service handles the most complex step, but a few post-installation procedures are often necessary. Follow these steps for a successful replacement.
- Safety First: Always disconnect the negative terminal from your vehicle’s battery before starting any electrical work.
- Locate the PCM: On most compatible trucks and SUVs, the PCM is located in the engine bay, on the driver’s side, often near the battery or air filter box.
- Disconnect the Connectors: Carefully unlatch and remove the electrical harness connectors from the old PCM. Inspect them for any corrosion or damaged pins.
- Remove the Old Module: Unbolt the old PCM from its mounting bracket and remove it from the vehicle.
- Install the New PCM: Mount your new, pre-programmed PCM and securely reconnect the electrical harnesses. Ensure they click into place.
- Reconnect the Battery: Reattach the negative battery terminal.
- Perform Security Relearn: Your vehicle’s anti-theft system (Passlock/VATS) will likely need to be relearned to the new PCM. This procedure typically involves turning the key to the ‘ON’ position for 10-15 minutes, then off, and repeating two more times. Consult your vehicle’s specific procedure for exact steps.
- CASE Relearn (If Necessary): A Crankshaft Position System Variation (CASE) relearn may be required to clear a P1336 trouble code and ensure accurate misfire detection. This step requires a bi-directional scan tool and is often best performed by a professional mechanic.
Verified Vehicle Compatibility
This module is a direct replacement for service numbers 89017750, 12582605, 12589463, 12602802, 89017734, and 28042802. It fits a wide range of GM trucks and SUVs. Please verify your vehicle is on the list below. Note that for some 2004 models, matching the ID number 12602802 is critical.
CADILLAC ESCALADE, ESV, EXT 03-06
HUMMER H2 03-07
ISUZU ASCENDER 03 (5.3L)
CHEVROLET SSR 03
CHEVROLET SILVERADO 1500, 2500, 3500 03-07 (Classic Style)
CHEVROLET SUBURBAN 1500, 2500 03-06
CHEVROLET TAHOE 03-06
GMC ENVOY XL 03 (5.3L)
GMC SIERRA 1500, 2500, 3500 03-07 (Classic Style)
GMC SIERRA DENALI 03-07 (Classic Style)
GMC YUKON & YUKON XL 1500, 2500 03-06
TRAILBLAZER EXT 03 (5.3L)
…and more. Please check the full list for specific options and engine sizes.
Frequently Asked Questions About Your New PCM
Frequently Asked Questions
Do I really need to provide my VIN?
Yes, absolutely. Providing your Vehicle Identification Number (VIN) is the only way we can program the module with the correct software and calibrations for your specific vehicle’s engine, transmission, and options. This is essential for proper function.
Is this a simple plug-and-play part?
It’s very close. We handle the programming, which is the hardest part. However, you will still need to perform a security relearn procedure after installation for the vehicle to start. This can usually be done without special tools.
What is a CASE relearn and do I need to do it?
A CASE (Crankshaft Position System Variation) relearn synchronizes the new PCM with your engine’s crankshaft position sensor. If it’s not done, you may have a Check Engine Light with code P1336. While the vehicle will run, this procedure is recommended and requires a capable bi-directional scan tool.
Will this fix my transmission shifting problems?
In many cases, yes. The PCM also controls transmission functions, including shift points and line pressure. If your transmission issues are caused by a faulty computer, this new 2003 TrailBlazer EXT PCM will resolve them.
What if I order the wrong part?
We strongly encourage you to verify your part number and check the compatibility list before ordering. Because these units are programmed to a specific VIN, returns can be complicated. If you’re unsure, contact us with your VIN, and we’ll be happy to help confirm fitment.